1. Field of the Invention
The present invention relates generally to the optical scanning of indicia, particularly although not exclusively to barcode scanning. More particularly, the invention relates to a scanner which is suitable for use both in a fixed mode and in a hand-held mode.
2. Discussion of the Prior Art
Prior art barcode scanners and decoders have generally employed a fixed working range, which in some products is typically seven or eight inches. Under some operating conditions, a barcode which is not located within the defined working range can result in an erroneous decoding of the barcode, or alternatively multiple different decodes of the same barcode. Clearly, neither of these is acceptable as they are likely to result in erroneous data entries.
This lack of flexibility in many prior art scanners becomes particularly acute when the user needs to scan barcodes on a variety of different objects, some of which may be close to the scanner and some of which may be further away. At a supermarket point-of-sale, for example, most of the items to be scanned may easily be accessible to the checkout operator as they pass by on a checkout conveyor. However, occasional bulky items may not fit onto the conveyor and it may be inconvenient and perhaps very difficult to bring such items close enough to the scanner for the barcode symbol to be read.
In an effort to address this problem, U.S. Pat. No. 5,324,924, assigned to the same assignee as the present invention, describes an arrangement in which the user can selectively determine the working range of the barcode scanner. If the user attempts to scan a barcode symbol which is too far away to be read, the scanner indicates this fact, and the user then changes the working range by scanning a special control barcode symbol. The control barcode symbol instructs the scanner to use a different software routine, which is better optimized for scanning barcode symbols which are far away from the scanner.
A difficulty with such an arrangement is that the user has manually to scan the control barcode symbol whenever the working range is to be changed. This is somewhat inconvenient for the user, and, unless the user is experienced, can easily be forgotten, resulting in lower than optimal efficiency at the point-of-sale.